Sound wave diffuser



Feb. 13, 1951 L. M. STARK 2,541,946

SOUND WAVE DIFFUSER File d June 1, 1948 Z'Sheets-Sheet 1 ji gi a 1 Z7 Z0 awe/Mm lavrerzc]! Stark Feb. 13, 1951 STARK 2,541,946

sounn WAVE DIFFUSER Filed June 1, 1948 v 2 Sheets-sheaf 2 Law'en ceMSZ'ar/i Patented Feb. 13, 1951 0 NIT E o STA-T ES Q FF-ICE SOUND WAVE DIFFUSER;

Lawrence ML j Stark, Alexandria ya.

ApplicationJune .1; .1948,= Serial'No.:30,4Q6

7 Claims, (01. 131 31),

Thistinvention relates;

sound and it isza particular, object of the inventionto provide acmeans for generallyimproving the reproduction ofasound from.- loudspeakers such as are usually associated with fullfrequency,

range radios, phonographs .and the. like.

It is well known that..the. sound emanating, from the diaphragm.of.arreproducerconsists of many: different audible.frequencies,l the .ghighest. of which are produced by the .pOl'jJiOIl .of the dia phragm nearest :to .the center 5 and :the lowest by the-portion farthest from the. center; It.:is also,

well known thatthe.v highest of. the frequencies are transmitted much in the form of.;a beam, and

in high quality radios and phonographsafiording full range reproduction, audio-:frequency vibrations extendin to 15,000. cycles.- per. second. are c. often encountered. It is -in.:the. highenfrequencw portion of theaudible spectrum, that. is,. from.

4,000 to 15,000 cycles per second,: that. this..beam

becomes verypronounced. Adistener 'located'in front ofsuch a reproducer will :receive thethighq. frequency component of speech: or .1 music; with 1 undue emphasis, while one. located at the..'side.-,. of such reproducer: will i not-v receive this ;.hig1r.'-.'1

frequency component in sufiicient emphasis It is -a further obj ect of :the present invention-1:.

to provide a device which-maybeaeitherz incorporated into the loud speaker assembly ias asunit by the manufacturer for use-with radios, phone-2.. graphs and the like or. for addition .to: and...em-. ployment with'the loud speaker, which will effect a dispersion anddiffusion of a large. proportion of F the high frequency vibrations .in: such a, mans; 5 1 ner-that a listener'positioned to oneside. of the... reproducer as well asinfront thereofwill receive; the proper proportion of the-high1 and low; free.

generally-to the .art-pf. reproducing recorded and; radiotransmitted quency vibrations with theproper .emphasisfor the-fullest-enjoyment of the same;v

Another object of the invention is; to provide a 1 I device designed to be sdisposedzin. front. of the cone-:of aloudspeaker, which isso constructed; thata :large proportion of :the: 1 axially. directed beamofhigh frequency vibrations .will not only; be deflected laterally butwill beiannedtout S0381;

to bespread to the fullest extentthrough a wide area.-

Still another object-of the invention is. to pro-.1

vide a device of'Ithe character stated wherein an;

auxiliary means is provided for-deflecting a portion of; the high frequency vibrationsnot dis-u persed by the preceding means wherebya second. and independent band or pathof deflected vibra tionsis produced.

Still-another ,oloiect:oflthadnvention .isuto pro-a vide.,;a device of trie -character statedswhich designed. ;,to permit; the, proper. amount of high equen y-J i nationato. be deflected 1 and diffused: and at [the samettixne permit a-proportionoithe. high.frequencywibrations to, pass; through.-:.unde: 4. nested-and. undiffuseds.

Still another. objectjof the invention. is .to pro-3,. vide ran.- efficient;andinexpensiveidiifusing devices.- fortproducinggthe results-stated;which. is .readily..: adaptable-;;.to many typesv and sizes 7 of; 10 11111.;- speakers.

The 1inYention..-wil1 ;be ;;best understood-.from a consideration} o1i,-.the following; detailed descrip;.;

tion takfinin connecti n with thea company ng drawingsgforminge;a; part of, the specification,- withsthepunderstandmg. however,.that the invention is not to be limited to the exact details of construction hown. and describedv since obvitlus modifications will occurv toa; person skilled gin the; art;

InthedraWi-ngsz Figure 1 is a View in section in an axially exn n p ane hro h a dev e on uc ed; in cce d n a ith e.ip ntsinvem onr win s es meim p l ed ositio etw en impos t: aloud speaker-unit and meun nspans t Fi u e 21 a v w n-fin; nlaredQa1eert Y inelevation. and part y nse ion shpwinsi PeP1.-.-

the manner inwhich thehigh frequency vihrae ions a es r e ia dad fiusedur 3.. new. r 1 Y t 9I ut nd. f h evice-. Figure see in letat q he n.r nd; thedsvice-i F surefi say swshewie iii-se arate a d. i de-: lell i pn hei sne nde uter poses... the same ein .02 n er d; e- F ure 6 s iv ew. n-per peetiyepfth e -e enr romfihe soe z u id- The diffuser device of the present invention is interposed between the speaker cone and the baffle board as shown in Figure 1 and such device is generally designated D.

In accordance with the present invention the diffuser comprises a cylindrical body ll] having formed integrally therewith the encircling end flanges ll. As shown in Figure 1 one of these flanges is positioned against the rear side of the baffle board B and is secured thereto in a suitable manner by securing elements 12 while the other flange has positioned thereagainst the mounting flange S of the speaker and these flanges are joined together by securing elements l3 of suitable character.

Supported n the axial center of the cylinder III which provides a sound Wave guiding passage from the speaker cone to the baffle board opening B, is a diffusing cone which is generally designated [4 and which may be formed of metal or any other suitable material as also may be the cylindrical housing body 10. This diffusing cone I4 is maintained in proper position or coaxially in the cylindrical housing body It, by means of the radial mounting arms or struts which extend from the base portion of the cone radially outwardly and connect with the wall of the cylindrical body l0, and the rear or inner end arms l6 which are here shown as two in number and which extend radially from the apex portion of the cone outwardly for connection with the body l0.

As is readily seen in Figure l the diffusion cone ll which is actually in the form of a frustum and which is both hollow and open at its base and apex ends, has the apex end disposed toward the speaker cone, and is, of course, coaxial therewith.

l'he diffusion cone I4 is constructed with its wall of longitudinally arcuate or convex form and the surface curvature is of a prescribed or definite radius depending upon the diameter of the speaker cone.

Formed through and extending longitudinally of the cone 14 are slots i! which extend through very nearly the entire length of the cone. Between these long slots or full cone length slots H are shorter longitudinally extending slots I8 which, in addition to being shorter than the slots H are of smaller width. lhese short slots l8 are disposed at the small end of the cone and extend only through a portion of the length thereof, preferably approximately through one fourth the length of the cone. Preferably there are eight of the long slots and eight of the shorter slots, the shorter slots being positioned centrally between the long slots and all of the slots being equidistantly spaced around the cone.

Disposed within and concentric with the cone I4, is the smaller inner cone which is generally designated l9 and which is open at its apex and base ends as is clearly shown in Figures 1 and 2.' This smaller inner cone has its wall straight throughout as opposed to the outward curvature or bow longitudinally of the wall of the larger outer cone.

The outer cone is positioned with the plane of its base flush with the plane of the forward end of the cylinder Ill and the smaller inner cone I2 is also positioned to have the plane of its base in a common plane with the base of the larger cone and the end of the cylinder as is also clearly shown in Figures 1 and 2.

It will also be readily seen that the diameter of the base of the smaller cone is materially less than the diameter of the base of the larger cone and the smaller cone is maintained in coaxial relation with the larger cone and the cylinder, by means of the three radial arms 20 which connect the base portion of the small cone with the base portion of the large cone as best seen in Figure 6.

The smaller cone is which has its apex portion cut off and which accordingly is actually a frustum of a cone the same as the larger cone M, has formed through the wall thereof the eight longitudinally extending slots 2|. Eight slots are here specified for the smaller cone because this is the number of long slots formed in the larger cone [4 and the cones are relatively positioned so that the slots of the smaller inner cone will be in the radial planes of the long slots of the larger cone as is clearly shown in Figure 7. This arrangement permits a desired proportion of the sound waves to pass directly through the two cones and in a straight line outwardly from the speaker.

In Figure 2 the broken lines designated 22 represent one half of all of the high frequency waves passing from the reproducer or speaker S and entering the high frequency diffuser device of the present invention. From point 23 to point 24 the proper portion of the highest frequencies striking the surface 14, is deflected. Another portion passes through the short slots l8 and is deflected by the surface of the smaller inner cone I9 approximately from point 25 to point 26. Still another portion passes through both cones undefiected by reason of the radial alignment of the slots l1 and 2 I.

As a result of placing the slot I! and 2| in line with one another the short slots l8 will be in a position, relative to the small cone [9, as between slots 2| of the small cone and the effective lateral area covered by slots [8 will be approximately from point 25 to point 26 on the smaller cone l9. Some deviation from the foregoing is permissible as regards the number of longitudinal slots, their size and placement. However it has been found that the best overall results are obtained when the following specifications are employed. In giving these specifications however, it is to be understood that there is no intention of limiting the invention to the same.

In a construction where the overall diameter of the cylinder is approximately fifteen inches including the flanges H the diffusing cone l4 will be approximately four and three-quarter inches in diameter and five inches long. The diffusing cone I9 is approximately two and threeeighths inches in diameter and two and threequarter inches long. The smaller end opening of the larger cone I4 is approximately one inch in diameter while the diameter of the small open ing of the smaller cone 19 will be approximately five-sixteenths of an inch in diameter. I

With the dimensions given the curve of the wall of the larger cone I4 will have a radius of approximately nineteen inches and this radius would be correspondingly reduced or decreased in diffusers of smaller design.

The width of the slots in the cones is made in accordance with the amount of the radiations.

which it is desired to have pass directly through the diffuser or in other words in accordance with the amount to be deflected. A desirable dimen-.

sion for the slots in a diffuser of the approximate dimensions above set forth is one-firth of an inch width for the slots I1 and approximately one-eighth of an inch width for the shorter slots assumes 5. I8 located thereb'etween. Foritheas'maller cone 1 5 ,the, width, o f ;the. slots. isflthei same ,asfiQijhe slots 11 of the larger cone. Withslots', ofthe sizes given and with the number shown it is found that approximately eighth-ninths-of'all of the high frequency speaker radiat ons are deflected and-dispersedwhile one-ninthofthe same pass through the cones undefiected. Accordingly -thc designherewith given follows this pattern;

It'will beqreadily apparent from-the foregoing;

that since theangle of the deflected wave jean-3 proximately the same as that of the incident wave and since the angle-of "incidence-is progressively changing from the apex-.tothebase of the/900115,

Wa t fo lows hat heane esc f. the defle t d vibrations from the surface of this cone [4 are likewise changing as they are followed from the apex to the base of said cone. This results in a much more thorough and complete dispersion of the deflected high frequency sound vibrations than could possibly be obtained through the employment of a deflecting surface without curvature.

In the illustration it will be seen that the length of the cylinder or mounting rim is very nearly as great as the length of the larger cone 14. This construction or arrangement is desirable for the use of the diffuser device with dual speakers employing a coaxially mounted cone tweeter within the large cone woofer.

In the type of coaxial speaker incorporating a compression-type high frequency unit together with a cone-type low frequency unit a shorter or narrower cylinder will be used since there is usually more space within the large speaker to accommodate a greater portion of the larger diffusing cone [4.

I claim:

1. The combination of a loud speaker and a sound wave diffuser unit therefor, said unit comprising a hollow body open at both ends, means for supporting said body at the front end of said speaker, a hollow frustum of a cone open at both its apex and base ends, means supporting the cone within said body coaxial alignment with the speaker cone with the open apex end directed into the speaker cone, said first cone having a longitudinally convexed surface covering a circular area around the axis of the cones of a materially smaller radius than the radius of the speaker cone to have the major portion of the waves making up the high frequency beam impinge against said surface, and said first cone having longitudinal slot openings therein for the passage of a portion of said beam therethrough.

2. The combination with a loud speaker as set forth in claim 1, with a second and smaller hollow frustum of a cone open at its apex and base ends, supported coaxially with and within the first mentioned cone, the base ends of the two hollow cones being in a common plane perpendicular to the wave beam.

3. The combination with a loud speaker as set forth in claim 1, with a second and smaller hollow frustum of a cone open at its apex and base ends, supported coaxially with and within the first mentioned cone, the said smaller cone having its apex end extending in the same direction as the apex end of the first mentioned cone, the walls of the cones being separated a substantial distance, and slots formed through the walls of the two hollow cones and extending longitudinal- 1y thereof.

4. The combination with aloud speaker as set fortheiin claim 1, with aisecond: and Jsmaller'hol low frustum of avcone open at its apex-and :baserc ends, supported i-coaxiallywith and Within'thee first mentionedncone, the said smaller cone having its.:apex-..endvextendingin the same -direction:- asthe apexend ofthe first mentioned cone-the a walls 1 of thecones :being separate-d a substantial? distance; andzslots formed through thexwalls of; the two h'ollow: .cones and extending longitudinal-,- ly-= thereof certainrof the slots-of the first men., tionedconerbeingiin'linewith slots of the smaller; coneiandotherrslots of the firstzmentionedconezz. beingingaline longitudinally of :the comes with .1 unslotted portions ofthe smaller cone;

5. A diffuser unit foradeflectingr'sound waves; of high.zfrequencyegenerated by a loud speaker, comprising a cylindrical open ended body adapted to be mounted at the front end of a speaker, a

hollow frustum of a cone open at its base and apex ends mounted within said body in a manner to dispose the same in coaxial relation with and in front of the speaker cone with its apex end directed into the speaker cone, said first cone having a longitudinally convexed wall with openings therein for the coaxial passage of a portion of the high frequency waves therethrough, a second hollow frustum of a cone of materially less length and less overall diameter than the first mentioned cone, means supporting the second hollow cone coaxially within the first mentioned cone with its apex end extending in the same direction as the apex end of the first mentioned cone, the second mentioned hollow cone having its apex and base ends open, and said second hollow cone having openings in the wall thereof in alinement with the openings in the wall of the first mentioned cone whereby a proportion of the high frequency waves may pass through the two cones coaxially therewith, the said openings in the two hollow cones being in the form of relatively long slots extending longitudinally of the cones through substantially the full length thereof, and other slots formed longitudinally in the first mentioned one of the hollow cones adjacent to the apex end thereof and in line longitudinally of the cones with unslotted areas of the second mentioned cone.

6. A diffuser unit for defimting sound waves of high frequency generated by a loud speaker, comprising a cylindrical open ended body adapted to be mounted at the front end of a speaker, a hollow frustum of a cone open at its base and apex ends mounted within said body in a manner to dispose the same in coaxial relation with and in front of the speaker cone with its apex end directed into the speaker cone, said first cone having a longitudinally convexed wall with openings therein for the coaxial passage of a portion of the high frequency waves therethrough, the deflector being provided with longitudinal slots through which a portion of the beam waves pass, and a second deflector formed to provide a straight deflecting surface disposed oblique to and in the path of certain of the beamed waves passing through the openings of the first deflector, said second deflector having openings in line with certain of the openings of the first deflector whereby certain of the beamed waves may pass therethrough.

7. A diffuser unit for deflecting sound waves of high frequency generated by a loud speaker, comprising a cylindrical open ended body adapted to be open at its base and apex ends mounted within said body in a manner to dispose the same in coaxial relation with and in front of the speaker cone with its apex end directed into the speaker cone, said first cone having a longitudinally convexed Wall with openings therein for the coaxial passage of a portion of the high frequency waves therethrough, a second hollow frustrum of a cone of materially less length and less overall diameter that the said first cone having its apex and base ends open, a spider supporting said second cone coaxially within said first cone, and said second cone having openings in the wall thereof in alignment with the openings in the wall of said first cone whereby a portion of the high frequency waves may pass coaxially through both of the cones and a portion thereof obliquely outward through said openings.

. LAWRENCE M. STARK.

REFERENCES CITED The following references are of record in the file of this patent:

5 UNITED STATES PATENTS Number Name Date 1,436,080 Blieberger Nov. 21, 1922 1,481,634 Thomas Jan. 22, 1924 4 1,486,650 Foley Mar. 11, 1924 3 2,033,337 Harmer Mar. 10, 1936 2,179,840 Bucky Nov. 14, 1939 FOREIGN PATENTS Number Country Date 5 791,142 France Dec. 4, 1935 

